Telephone magnet system



Oct. 30, 1928. M 1,689,948

R. 'r. KINGSFORD ET AL TELEPHONE MAGNET SYSTEM Filed July 2, 1925 v 2 Sheets-Sheet 1 warranty R; T. KINGSFORD ET AL TELEPHONE MAGNET SYSTEM Filed July 2, 1925 2 Sheets-Sheet 2 g &

NVE TORS' w BY I Q 7 ATmRNEY Patented Oct. 30, 1928.

UNITED STATES 1,689,948 PATENT OFFICE,

anaemia. n or wimco'ra, m WILLIAK a. means, or

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Application fled July 2,

Our invention relates to the magnet system of. telephonic apparatus for converting sound-representin current into sound, or vice versa and particu arly to magnet systems for amplifying telephones, loud speakers, radio speakers or the like, utilized in connection with radio receivin apparatus.

In accordance witfii our invention, the magnetic system comprises a' field yoke or frame, preferably permanently' magnetized, having pole pieces whose pole faces are accurately trued or determined, procured .by grinding or equivalent operation, and which are in substantiall the same plane, in combination, witha relatively stifi or rigid vibratile arma-' ture member or reed having at its opposite p0 p a Fig. 4 is a horizontal sectional view, on

ends similar accurately trued or determined faces, one 'of which at the free end of ,the armature member is spaced from the trued surfaces of the pole piecesiland the other of which at the other end of t e armature mem-' her is secured against an accurately trued or ound surface on theoke or magnet frame itself, or, and preferab y, an accurately trued mem more particularly, of arwidth servin phra or ground surface of a member rigidly secured to the magnet frame or oke and serving to space the fixed end 0 the armature member from the yoke or frame,

Further in accordance with our invention, the oke or ma et frame has a bridging her, prefera ly inte al therewith, extending transversel .o the longitudinal ali ment of the pole pieces, adjacent their en and displaced laterallyfrom the plane of the yoke cl? field frame and serving as a support or abutment for an "adjusting screw or' equivalent, of non-magnetic material, engaging the pole pieces and serving nicelyto ad ust the air gap-between them and the free end of the vibratile armature member; and the brid 'ng member is to hol or confine the ct coils or win ings. urther in accordance with our invention the greater energy available for movement of the telephone dia hragm, resulting from our construction, ena les the ratio of amplitude of' vibration ofthe vibratile armature member to the. amplitude ofvibration of the diato besubstantially unity,even when the iaphragm is conical and of relatively lar diameter.

8dr invention is further characterized by a method of operating upon and bling the component arts of.

ig. 1 is a vertical sectional 1m. lerlal I0. 415031.

in elevation, of apparatus embodying our in- VOlltlOll. a v

Fig. 2 is a front elevational view; of the ma etsystem. H a ig. 3 is a front elevation of the magnet enlarged scale, partly in plan, taken on the line 4'4 ofFig. 2. i

yoke or framewithattached armature sup-.

the accompanying draw:

view, partly -Fig.- '5 a vertical "sectional view, on em. I

larged scale, partly in elevation, taken on the hue 5 -.-5jof ig. 2. i v

; The magnet system, its mounting and the mounting of the conical diaphragm, are of the general character disclosed'and claimed in prior application :Serial No. 32,875, filed M ee eeaefe'rring to the drawings, l-isa'base or stand to whichis secured by screw 23; bracket member 3, to which is secured'the upwardly extendi arm 4,-terminating in the supportinglmem r 4, to which is secured by screws 5 t e substantially recta lar frameo'r yoke 6 of the magnet system, suitable spacing members 7 intervening between the frameor oke 6 and the-support 4'through holes inw ich the-screws 5 extendandhave applied thereto on the rear of the support 4 the nuts 8. Secured to the frame or oketi by the same screws '5 are. the inwar extending poll. ieces 9, in alignment wit each other, and tween whose innerends is left an air gap. The ole pieces 9 may be of any suitable ma-j teria but preferabl of Swedish iron or silicon steel. Surroun ing the pole pieces 9 are the windings or coils C traversed b the voiceor sound-representing current, suc asexists, for examplei in the anode circuit of' a .dey field upon the vibratile armature mem-.

her 10, of suitable material, and preferably of silicon steel whose hysteresis and eddy current losses are relatively low.

The yoke 6 is preferably permanently magnetized, and is preferably composed of chrome or tungsten magnet steel. It has poles of opposite signs at opposite ends thereof adjacent the points of attachment thereto of the pole pieces 9, 9, whereby at the inner and adjacent ends of the pole pieces 9 are exlliibited opposing northand south magnetic Substantially mid-way between the ends of the yoke or frame 6 there is a hole 11 therein, in which is riveted the hollow or tubular shank 12 integral with the spacer member 13, of any suitable material, such as iron or steel, into which is threaded the screw 14 extending through a hole in the vibratile member 10 to rigidly secure it to the member 13 and therethrough to the yoke or frame 6: The member 13 serves also as an abutment for the stiff reed or armature 11 about which it may flex or bend under the influence of the soundrepresenting current.

Integral with the yoke 6 is the bridging member 15, offset from the plane of the yoke 6 on that side thereof opposite the armature 10. Member 15 is of greater width'than the armature 10, and preferably of such width that it confines the coils C, C between itself and the sides of the yoke 6', whereby the sides of the yoke 6 and the member 15 serve as abutments preventing substantial longitudinal movement of the coils C upon the pole pieces 9.

The bridging member 15 serves also to support the adjusting screw 16, preferably of brass or non-magnetic material, threaded therethrough and having a flat end engaging the adjacent ends of the pole pieces 9, 9, and bridging the gap between them. Adjustment of the screw 16 serves to flex the inner ends of the pole pieces 9, 9 toward the adjacent face of the free end of the vibratile armature 10 nicely to adjust the effective air gap between them. Once the screw 16 is adjusted, it is locked by the nut 17.

Threaded into the vibra-tile member 10 is the pin or rod 18, to which is fixedly secured the air-vibrating member as the conical diaphragm or tympan 19, of relatively large diameter, preferably upwards of six inches. The diaphragm has at its center the sheet metal conical structure 20 to which the diaphragm proper is secured, and the member 20 is provided with a sleeve 21 through which is threaded the screw 22 engaging the rod 18.

The diaphragm is supported solely by the magnet system, and particularly by the yihratile armature 10 thereof. The pin 18 may be attached to any suitable point along the armature 10, and preferably at such point thereon that the ratio of amplitude of vibration of the cone 19 to the amplitude of vibration of the armature 10 at that part thereof I pieces so in about the middle of the width of the pole pieces 9 is substantially unity. As indicated, the rod 18 may be attached to the armature 10 at the middle of the width of the pole pieces 9, though it will be understood that its position may be nearer or more remote from the fixed end of the member 10, and in those cases also the aforesaid ratio may vary slightly from unity.

The cone 19 at its periphery is free and unconfined. To shield or guard the cone 19, which may be constituted of paper or thin sheet metal, there may be provided the housing or guard structure 23, Fig. 1, extending around the periphery of the cone 19, and extending also to either or both sides thereof, but substantially spaced therefrom to permit free vibration of the cone throughout and at its periphery. The shield or housing structure 23 may be of sheet metal carried by or integral with the several arms 4.

The yoke 6 may be punched or stamped from sheet material of desired thickness, and the bridging member 15 offset from the plane thereof by operation thereon by punch or die structure. Thereafter the member 6 is hardened preparatory to its permanent magnetization.

We have found that the operating characteristics of the magnet system herein described are materially improved by recourse to refinements which, so far as we are aware, are novel in a system of the character described.

Spacer or abutment member 13 is riveted or secured to the yoke 6, and thereafter the face (1 thereof adjacent the armature 10 is trued, as by grinding or equivalent operation, to effect a smooth true surface preferably substantially parallel to the plane of the yoke 6. Preferably, however, this grinding of the face of member 13 is accomplished at the same time the faces of the poles 9 are ground, as hereinafter described.

The coils C, C are placed in their respective openings 0 between the bridging member 15 and the sides of the yoke 6, the pole pieces then slipped through their open centers, and the screws 5 placed in position and the nuts 7 applied securely to hold the pole pieces 9 at their outer ends against the sides of the yoke 6, with the two pole pieces in substantial alignment with each other. With the pole their operative position upon the yoke 6, their inner ends are ground or similarly operated upon on their faces I) presented to the armature 10, to true those faces and bring them substantially into the same plane. During this grinding or equivalent operation it is preferred that the ends of the pole pieces 9 be slightly flexed outwardly by adjustment of the screw 16 toward the right, Fig. 5. The face of the abutment 13 is preferably ground at the time the pole pieces 9 are ground, thereby requiring but a single clamping of the III member 6 and attached machine.

With the pole pieces 9 and coils C in place, and either before or after the grinding of the pole pieces, the hardened steel yoke 6 is magnetized, and thereafter preferably artificial- 1y aged. v

The vibratile armature member 10 is similarly ground or operated upon at both ends, at its surfaces and d, on its side adjacent the yoke 6 and pole pieces 9. It is thereupon laced in position upon the member 13 with its ground surface 0 in contact with the outer ground surface a of the member 13, and there rigidly secured by the screw14. The ground face d at the free end of the armature is accordingly disposed opposite the ground faces b of the inner ends of the pole pieces 9, defining therewith an accurately determined air gap whose length is thereafter adjusted, if necessary, by further adjustment of the screw 16 either to relieve the previous tension placed upon the pole pieces during the, grinding operation, or to press them further toward the free end of the vibratile member 10. The air gap between the surface d of the member 10 and thesurfaces b parts in the grinding of the pole pieces 9 is very short, and materially shorter than the gap between the adjacent ends of the ole pleces 9. This air gap is of substantial y equal length throughout, due to'the grinding of the surfaces of the pole pieces and of the free end of the armature. And "parallelism between the ground ture 10 ground parallel to each other, the

surfaces d and b are quite accurately parallel to each other and effect an air gap of uniform len h, from which results a more uniform an more intense magnetic field in the short air gap, other things being the same; and with a relatively stronger magnetic field or more powerful action upon the armature 10 the latter may be relatively thicker, and,

therefore less easily flexed, and therefore partaking of smaller amplitude of vibration, substantially equal to the amplitude of vibration suitable for a large cone diaphragm, and this relation makes more readily obtainable the substantially unity ratio of amplitude of vibration of the conical diaphragm to the amplitude of vibration of the vibratile member 10 at its region approximate the middle of the width of the polepieces 9.

While a spacer member 13 is utilized, with its surface a ground parallel to the faces I) of the pole pieces, it will be understood that the member 13 may be riveted, secured to or integral with the armature 10, in which event the surface of the magnet frame 6 engaged by the member 13 will be ground parallel to the faces I; of the pole pieces, as well as the face of the member 13 engaging such ground surface of the magnet frame 6.

It will further be understood that a spacer member may be omitted and the end of the armature 10 secured directl against the yoke 6 with their engaging sur aces ground parallel to the faces 6 and d of the ole pieces and armature member, respective y.

What We claim is: a

1. A telephone magnet system comprising ground pole face, and a diaphragm of large area having small amplitude of vibration in unconfined air actuated by said vibratile armature bar.

2. A telephone magnet system comprising a magnet frame, pole piece structure secured thereto at its one end and having at its other end a ground pole face, a vibratile armature bar secured adjacent its oneend to said magnet frame and having at. its free end a ground face disposed adjacent and substantially arallel to saidv ground pole face, and a diap ragm of large area having small amplitude of vibration in unconfined air actu ated by said vibratile armature bar.-

3. A telephone magnet system comprising a magnet frame, pole piece structure secured thereto at its one end and having at its other end a ground pole face, a vibratile armature bar secured adjacent its one end to said magnet frame at a face ground parallel with said ground pol face, said armature barfhaving its free end spaced from and disposed parallel with said ground pole face, and '21 diaphragm ofla-rge area having small amplitude of vibration in unconfined air actuated by said vibratile armature bar.

4. A telephone magnet system. comprising thereto at its one end and having at its other end a ground ole face, a vibratilearmature bar secured adjacent its one end to said ma net frame at a face ground parallel with sald ground pole face, said armature bar having at its free end a ground face parallel with the face at its attachment to said magnet frame, and a diaphragm of large area having small, amplitude ofvibration 1n unconfined air actuated by said vibratile armature bar.

5. A telephone magnet system comprising amagnet frame, pole piece structure secured thereto at its one end and having at its other end a ground pole face, a vibratile armature bar secured adjacent its one end to said magnet frame and having at its free end a ground face disposed adjacent and substantially parallel to said ground pole face, said ata magnet frame, pole piece structure secured tachment of said armature bar to said magiet frame comprising contacting ground faces parallel to the ground faces on the free end of said armature and said ole piece structure, and a diaphragm of arge area having small amplitude of vibration in unconfined air actuated by said vibratile armature bar.

6. A telephone magnet system comprising a ma et frame, pole pieces therefor extending grim opposite ends of said frame and having their inner ends spaced from each other, a vibratile armature bar secured adj acent its one end to said magnet frame and having its free end disposed adjacent the inner ends of said pole pieces and bridging the gap between them, said ma et frame having a member into al therewith extending transversel tosai pole pieces and spaced therefrom, an a member carried by said last named member and adjustable with respect thereto engaging said pole pieces to adjust the gap between them and the free end of said armature bar.

7. A telephone magnet system comprising a circumferentially closed magnet frame, pole pieces therefor extending from opposite sides of said frame and having their inner ends'spaced from each other, a vibratile armature bar' co-acting with said ole pieces, said magnet frame having a bri ging member integral therewithand extending transversely of said ole ieces, and a member carried by and a j usta le with respect to said bridging member enga g said pole pieces for adjusting them wit respect to said armature bar.

8. A telephone magnet system comprising a circumferentially closed magnet frame, pole pieces thereforeextendingfrom opposite sides of said frame and having their lnner ends spaced from each other, a vibratile armature bar co-a/cting with said pole pieces, said magnet frame having a bridging member integral therewith and extending transversely of said pole pieces and offset from the plane of said frame, and a member carried by and adjustable with respect to said bridging member engaging said pole pieces for adjusting them with respect to said armature bar.

9. A telephone magnet system comprising a magnet frame, pole piece structure therefor extending inwardly from one side of said g frame, a member integral with said magnet frame extending transversely of said pole piece structure, and a magnet winding on said pole piece structure confined between said member and said side of said frame.

10. A telephone magnet systemcomprising a circumferenti ally closed magnet frame, pole pieces extending toward each other from opposite sides of said magnet frame, magnet coils on said pole pieces, and a bridging member integral with said magnet frame extending transversely of said pole pieces and confinin said coils between it and said sides of said ame.

11. A telephone magnet system comprising a magnet frame, pole piece structure therefor, a co-acting vibratile armature bar whose free end co-acts with said pole piece structure, and means for securing said armature bar adj acent its one end to said magnet frame,com-. prising a member riveted to one of them, and an attaching member securing the other of them to said riveted member.

12. A telephone magnet system oomprisin a magnet frame, pole ieces therefor exten ing from opposite si es of said frame, said frame havin a hole intermediate its said sides, a mem r having a hollow shank riveted in said hole, and a vibratile armature bar secured at its one end to said member and having its free end disposed adjacent the feuds of said pole pieces.

13. A telephone magnet system comprisin a ma net frame, pole ieces therefor exten ing om opposite si es of said frame, said frame having a hole intermediate its said sides, a member havin a hollow shank riveted in said hole, an a vibratile armature bar secured at its one end to said memher and having its free end disposed adj acent the ends of said pole pieces, said armature bar and riveted member engaging each other at parallel ground faces, said armature bar and said pole pieces having their adjacent faces ound parallel with said first named groun faces.

14. A telephone magnet system comprising a magnet frame, pole piece structure therefor, a co-acting vibratile armature bar whose free end co-acts with said pole piece structure, and means for securing said armature bar adjacent its one end to said magnet frame comprising a member riveted to one of them, and an attaching member securing the other of them to said riveted member, said riveted member and armature bar engagin each other at parallel ground faces, the adjacent faces of said pole piece structure and of the free end of said armature bar ground parallel to said first named ground faces.

15. In the production of a telephone magnet system, t e method which comprises securing a pole piece at its one end to a ma ct frame, grinding a face on said ole piece, rindin a face on said magnet ame parallel wit the ound face on said pole piece, grinding para lel faces at the ends of an armature member, and securin said armature member at its one end with its ground face thereat in. engagement with the ground face on said magnet frame to osition the ground face at the free end of said armature member adjacent to and parallel with the ground face on said pole piece.

16. In the production of a telephone magnet system, the method which comprises securing a pole piece at its one end to a III 0 onsaidma magnet frame, slightly defl the free on o f'said le iece grindi a aceonsaid free end of ai pole piece hile deflected,

grinding a face on said magnet frame .parallel 5 with the ground face on said 1e piece, grinding parallel faces at the en of an armature member, and securing said armature member at its one end withits ground face thereat in engagement with the ground face at frameto ition the ground face at the cc and of sai armature member adjacent to and parallel with the ground face on said pole piece.

17. A telephone magnet system comprising 7' a magnet frame, pole (pieces therefor extending rom opposite'si es of said frame and,

having their inner ends spaced from each other, a vibratile armature bar co-acting with said pole pieces, said magnet frame having a member integral therewith and extending transversely of said ole ieces, and a membercarried by and a justa ble with respect to said magnet frame member engaging said pole pieces for adjusting them with respect to said armature bar.

RUSSELL Y .H. RICHTER.

T. KINGSFORD.- i 

